It is known that because of its frequency and gravity, pulmonary embolism is a major medical problem; it threatens any patient suffering from phlebitis in the limbs in spite of frequently applied preventative or healing medical treatment. The nearly sole origin of embolism is in the venous network of the lower limbs and the pelvis, possibly with thrombosis extension in the caudal vena cava. Already for a long time the idea has been entertained to obstruct the caudal vena cava to block the migration of the clot or embolus toward the heart and hence toward the lungs.
Initially the obstruction was realized by mere ligature of the sub-renal caudal vena cava, but this technique suffers from the drawback of precipitating in every case a massive thrombosis of the venous segment upstream of the ligature (due to the totality of the occlusion).
Therefore total ligature has been given up in favor of a partial blockage of the caudal vena cava. Presently two modes of the latter technique are being applied:
(a) either this partial blockage is placed inside the vein (filter, screen or other), which is a technique offering the advantage not to require general anesthesia but incurs the serious drawback of the risk of thrombosis upstream of the blockage and practically as large as in the case of total ligature (in particular due to introducing a foreign body into the vessel), or PA1 (b) placing an external and so-called extra-venous member around the vein, straddling the vein and partitioning its inside aperture into several channels of lesser bores.
The object of the present invention is a technique of the latter type wherein the partial occlusion of the vein or more generally of the vessel is achieved from its outside. An essential advantage of this technique is the appreciable reduction of risks of thrombosis.
The most improved and widely used device to implement this technique presently is a clip, in particular the ADAMS & DE WEESE clip developed in 1966; this polytetrafluoroethylene-molded clip comprises two arms forming a U, one of which is serrated. This clip is put in place on the vein so its two arms will straddle it and then is finally closed by a filament which binds said arms at their free ends (which ends are provided with notches for this purpose). The vein walls therefore are deformed and the presence of the teeth imparts to the inside aperture of the vein a partitioned shape, partly sealed, capable of stopping large clots or emboli while allowing the blood to circulate in the lesser cross-sectional channels (which are bounded by the clip teeth). In this manner dangerous pulmonary embolisms are prevented satisfactorily.
Nevertheless this device incurs a serious drawback. Its emplacement must be considered final, because new surgery to remove the clip would be much more dangerous; besides the typical risks of general anesthesia and the risks of thrombosis in any intervention, such new surgery would be applied to mauled tissues whereby the patient might incur serious wounds in the vein. Moreover if in spite of these dangers the clip were removed, at the end of the embolism period, it would practically be out of the question to resort to a third intervention to put in place another in the event subsequent pathology were to demand another emplacement of a partial occlusion; in that case the sick (who is especially vulnerable) would be defenseless against an embolic accident (or else be forced to resort to an intravenous occlusion technique with its own drawbacks).
Under these conditions the clip put in place in final form on the patient provides a partial but indefinite blockage the patient carries with him all his life. Now it has been found that the blockage subjects the patient to dangers related to permanent blood stasis upstream of the clip so long as it is in place (that is, well after the embolic period of the patient and all his life); chronic venous insufficiency syndrome in the lower limbs and danger of delayed thrombosis. This is the major drawback of the ADAMS & DE WEESE clip and of the analogue clips presently existing.
An object of the present invention to remedy this defect and to provide an improved device for partial occlusion and resorting to an extra-venous technique.
The main object of the device is to provide a device capable of preventing pulmonary embolism during the embolic period while allowing nevertheless to eliminate after this period the above cited delayed dangers.
To that end the object of the invention is to provide a device capable of providing a temporary partial occlusion of a vessel and of allowing the elimination of this occlusion at the selected time, and to do so without deep intervention (in particular without having to subject the patient to general anesthesia and without having to work again near the vena cava on previously mauled tissue).
Another object of the invention is to repeat the, occlusion effect after it was eliminated, at will, as many times as found necessary, in particular in the event of new pathology and to do this, as before, without deep intervention.
Another object of the invention is to facilitate the emplacement of the occluding member on the vessel.